1. Field of the Invention
The present invention relates to a thin-film transistor, a method of manufacturing the thin-film transistor, a liquid crystal display panel having the thin-film transistor, and an electro-luminescence display panel having the thin-film transistor. More particularly, the present invention relate to a TFT having improved electrical characteristics, a method of manufacturing the thin-film transistor, a liquid crystal display panel having the thin-film transistor, and an electro-luminescence display panel having the thin-film transistor.
2. Description of the Related Art
In general, a flat display device can be a liquid crystal display device, a plasma display panel device, a field emission display device, an electro-luminescence display device, etc. Typically, the liquid crystal display device and the electro-luminescence display device employ a plurality of thin-film transistors fabricated by forming a thin film on a transparent substrate. TFT Each thin film transistor includes a gate electrode, a source electrode, a drain electrode, a semiconductor layer, and an impurity layer. The gate electrode is formed on the transparent substrate. The source electrode and the drain electrode are formed over the gate electrode, separated from each other. The semiconductor layer is formed between the gate electrode and the source electrode, and between the gate electrode and the drain electrode. The impurity layer is formed between a portion of the semiconductor layer and the source electrode, and between a portion of the semiconductor layer and the drain electrode, respectively. The semiconductor layer may include amorphous silicon and the impurity layer may include amorphous silicon highly doped with ions.
A method of manufacturing the TFT is briefly illustrated as follows. The gate electrode is formed on the transparent substrate. The semiconductor layer and the impurity layer are formed over the gate electrode. Next, the source electrode and the drain electrode are formed on the impurity layer, and are separated from each other. Here, a little blank time (vacuum break) generally exists between a formation of the impurity layer and a formation of the source electrode and the drain electrode.
During fabrication, native oxidation of silicon may occur on an upper face of the impurity layer between the formation of the source electrode and the drain electrode, and the formation of the impurity layer. The native silicon oxide layer formed on the impurity layer increases a contact resistance between the impurity layer and the source electrode, and between the impurity layer and the drain electrode. The increase in the contact resistance is undesirable because it deteriorates electric characteristics of the thin-film transistor.